ultrahdr: do not select less accurate integer method during dct

At high quality setting, less accurate integer method can have
larger psnr drops. Switch to default setting

Bug: 286617381
Test: ./libultrahdr_app -p inp_p010.yuv -y inp_420p.yuv -w 1920 -h 1080 -o 0

Change-Id: Ide126b87262e1c9a20edca7873b6ca27fc52b2cb
diff --git a/libs/ultrahdr/jpegdecoderhelper.cpp b/libs/ultrahdr/jpegdecoderhelper.cpp
index fac90c5..6c3a8c1 100644
--- a/libs/ultrahdr/jpegdecoderhelper.cpp
+++ b/libs/ultrahdr/jpegdecoderhelper.cpp
@@ -242,7 +242,7 @@
         cinfo.raw_data_out = TRUE;
     }
 
-    cinfo.dct_method = JDCT_IFAST;
+    cinfo.dct_method = JDCT_ISLOW;
 
     jpeg_start_decompress(&cinfo);